Shop instrument



0 June 18, 1935.

H. F. PETERSON SHOP INSTRUMENT Filed May 11,

flaw-Fora flan/w ierwhandfleferaan 12;, M cum flTTor NE s Patented June 18, 1935 I 2,005,106 7 r snor INSTRUMENT Henry Ferdinand Beterson, Rockford, Illf Application May ll',1934, Serial No. 725,048 a Y am m -1 1 f 7 The invention relatesgenerally to measuring Connecting the arms Ill-and H is a means devices for use in machineshops for measuring which permits the arms tobeadjusted longitudiand'determining thecurvatureof arcs. nally, and'which holds'them in a pivotal rela The general object of the invention is to pro- ,tion, The axis of the pivot extends through the 5 vide' an instrument of new and improved conintersection of lines which areperpendicular to 5 struction which may be used conveniently in a and bisect the linesconnecting each pair of pins 7 machine shop for determining the center and I4. This means comprises a pair of slides l5'and radius of curvature of arcuate surfaces and to im the form of chann s s a y iv ng t measure and lay out arcs when the length, cen-I arms 10 and II and positioned to open toward 10 ter, or radius ofcurvature are known. each other sof'that the adjacent faces of the 10 The invention also resides in the construction arms are in contact; To pivotally connect the of the instrument which enables small arcs tobe rm h Sli s wand 16 ar r p i D laid out or measured and which facilitates a Vided with pivot pins "and I8 extending from justment of the instrument. the outerfaces thereof and rigidly attached 5 Other objectsand advantages will become apthereto as by welding, Supporting the pins l l 1 parent from the following description taken in and I8 is'aU-s apfi member 20 v n a Chane connection with the accompanying drawing,'in nel construbtmn, for d h l r which a p a 3 mounted between the ends of the U-shaped mem- Figure 1 is a perspective view of? device ember 'with the pins rotatably mounted in the re-' 20' bcdying the features of the-invention, showing spective ends. A nut 2! is threaded on one of the device applied to an arcuate surface. the pins preferably adjacent the inner faceof the Fig. "2 isa sectional view taken {substantially Ushaped member 20. To clamp the arms in on-the line 2-2 of Fig. 1. any desired position, the nut -2f is turned into Fig.--3 is asectional view taken on the line 3-3 ng m nt wi h the inn r fac f he'm mb r v to thesurface-to be measured. v L ends-of'the U shaped member. I

It is a known geometric principle that the in- The 'pivot Pins IT and l8' are'coaxial' and extersection of the perpendicular bisectors of any tend through the'intersection 'of the-perpendicutwo chords drawn across an arc determines the lar bisectcrsyof the lines joining the pins M *on of Fig, 1 and showing how the device .is applied 0, therebyfcrcing the arms toge h b n th 2 5 center and radius of the arc. The present ineach arm: 'I'he'aXisof'thepivot pinsisthusthe'at) vention utilizes'this principle "and, in the prec'e'nte'r'of curvature of thearcuate surface A, ferred embodiment shown'irr'the drawing, comwhen'all four pins I new simultaneously in com prises generally a pair of arms each of which is tact'with the arcuate surface. g f fashioned at one end to" contact the arcuate'sur- The radius of curvature of the arcuate surface face at two annularly spaced 'points defining a is, then, the distance fromthe axis of the pivot 3 5 chord of the arc. Connecting the arms is a pinsIT'and [8 to thearcuate surface. To-facilimeans which pivotally supports the arms and tate the determination of this radius, a scale -22; likewise permits longitudinaladjust'ment thereof is provided, which is preferably marked on the transversely of the pivotal axis which extends upper-face of the arm I0 and cooperates with the 40 through the intersection or the perpendicular adjacent'e'nd of the slide :15, indicated at 23; The 40" bisectors of the two chords. Combined with this scaleZZ is calibrated to give the radius enemy; by structure is a means for determining the angular the reading indicated at the end -23 of-the slide; measurement of 'the arc. v A similar scale is provided on the arm II to co 'As shown in the drawing, the two-arms, indioperate with the slide l6 so that both arms may cated generally at H! and H, are'T-shaped, each be set to the same radius, if the latter is already 45 comprising astem portion" I2 in the form of aknown; I rigid metal bar and ahead l3.- The head l3 1 Combined'withthe above described structure preferablyextends perpendicularly tothe stem isameans for determiningthe angular measureportion l2 and isfashioned to contact with an mentjof arrarc or for laying off a given angular arcuate surfacefsuch asthe surface A,at two measurement on the are after the center and 50 points; In the present instance, contact is made radius 'of curvature have been determined or ifby a pair of pins 14 mounted on the head portion they are known. As shown herein, said means I3. The pins I4 are spacedapart asubstantial comprises a pair of straight edges 24 and 25 asdistance in order tolocate the armaccurately sociated with the respectiveyarms. 'The two relative to 'the surface.

straight edges-are soconstructedthat they 91- 5 5 .the two straight edges may be moved into. close proximity to each other to measure small'angles without interference of the head portions.

Since the straight edge 25 is at one side of the arm II and cannot therefore be coincident with) the'perpendicular bisector of the line joining the pins I4 of the arm I I, the member2'l' is pivotally attached to the arm I I as by a rivet 28.1 To swing the member 21 on its pivot so that the. straight edge 25 will always extend radially, a' rod 30 is rigidly secured atone end to a member 21 and extends parallel to the edge 25. The other end of the rod 30 extends toward the U-shaped member and is there "supported so that it may be longitudinallyadjusted, while the arm II is so adjusted. The rod is, however, held in a predetermined relation to the pivotal axisof the arms. To'this end, an element in the form of a yoke 3| is mounted on the pivot pin I I adjacent the outer face of one end of .the U-shaped member 20. The yoke 3.I has a pair of downwardly extending spaced arms 32, which are apertured to receive the rod 30. The yoke also has a flange 33 adapted tobear against the outer face of the lJ-shaped member. Thus, as the arm s are swung relative f to each other, the straight edge will always be held ina radial position relative to the pivotal axis of the arms. To hold the yoke in place; a nut 31 is threaded on the outer end of the pivot pin I1. 3 vTo measure the angle between the straight edges, a protractor scale and a pointer are proof and integral with the slide I5 which supports the arm I0 having the fixed straight edge. The pointer, indicated at 36, is formed integrally with the yoke 3I so that it is angularly fixed relative to the rod andhence to the straight edge 25. In usingv the instrument; assume that it is de-. sired to determine the center and radius of curve..- ture of an arcuate surfacesuch as the surface A. The nut 2I is loosened so that the arms-land I land the rod 30 willbe free to swing and slide. The four pins I4 and the two arms are placed adjacent the arcuate surface, in the manner shown in Figsland 3, and the slides I5 and I6 'are moved along thearmsuntil all fourpins- I4 are inlcontact with the arcuate'surface at thesame time-and the chords definedthereby equidistant from the pivotal axis as determined by the scales 22., It is preferable to have the angle between the arms of substantial size to obtain accurate results, the maximum angle of course being deing with the end 23 of the slide I5.;

When it is desired to determine the angular measurement of an are or to lay ofi a given angle on the arcuate surface A, the arms are first set for the known radius of curvature andthen swun relative to each other to position the straight edges 24 and 25 as read on the scale 34. The straight edge 24, since it is coincident with the perpendicular bisector of the line joining the associated pins I4, is always in a radial position. The

straight edge 25 is likewise held in aradial'posi- .tionsince the rod1 30 is;ri gid therewlthand is pivoted 'on the axisof the arms I0 and I I.

. From the above, it will be apparent that I have provided an instrument suitable for use in a shop. By means of this instrument, the center and radius of curvature of an arcuate surface may be determined, and the angular measurement of the arc. may be determined or a given angle laid out. Theinstrument may be readily applied to the work and yields accurate results without the exercise of great care on the partof the operator. q I claim asmy invention:

1. An instrument of thecharacter described comprising, in combination, a pair of elongated arms, means for supporting said arms for pivotal adjustment about a common axis and also for longitudinal adjustment transversely of said axis, each arm having a transversely extending portion at its free end providingtwo contact points spaced apart a substantial distance transversely of the arm and adapted to be placed in contact with an 2. An instrument of the character described comprising, in combination, a pair of arms, -a pair of slides supporting said arms for longitudinal adjustment, means pivotally connecting said slides, means atone end of each arm constituting a pair of points adapted to be placed in contact with an arcuatesurfaoe, the lines joining the points of each pair being bisected by radii perpendicular to said lines, and means associated with said slides for indicating theangle between saidradii. .7

'3. An in'strumentof the character described comprising, in combination,-a pair of arms,-each I arm being fashionedatone end to contact an arcuate surface at two points to define chords thereof, a pair of slides respectively supporting said arms for longitudinal adjustment, a- U shaped member pivotally supporting said slides between its ends, and a single means operableto clamp said slides between the ends of said meme her and thereby hold said arms against longitudinal and angular movement. v I j 4. An instrument of I the character described comprising, in combination, a pair of arms each fashionedat one end to contact an arcuate surface at two points, a pair of slides supporting the respective arms for longitudinal adjustment, a U-shapedmember having said slidespositionejd between its ends, pins pivotally connecting said slides and the respective ends of said member, and a nut threaded onto one of said pins. andoperable toclamp said arms betweenthe endsof said member whereby to hold thearms against angular and longitudinal adjustmentw A 5. An instrument for determining thQCGIItGI.

and radius of curvature of an arcuate surface 76'- comprising, in combination, a pair of arms each fashioned to contact the arcuate surface at two points to define chords thereof, a pair of slides supporting the respective arms for longitudinal adjustment, means connecting said slides for angular adjustment about an axis passing through the center of curvature of said surface when said chords are equidistant from the axis, and cooperating means on said slides and said arms providing scales indicating radii of curvatures.

6. An instrument for determining the center and radius of curvature of an arcuate surface comprising, in combination, a pair of arms each fashioned to contact the arcuate surface at two points to define chords thereof, a pair of slides supporting the respective arms for longitudinal adjustment, means connecting said slides for angular adjustment about an axis passing through the center of curvature of said surface when said chords are equidistant from the axis, cooperating means on said slides and said arms providing scales indicating radii of curvatures, straight edges on the respective arms extending through said axis, and means associated with said arms and indicating the angular relation of said edges when said chords are equidistant from said axis.

'7. An instrument of the" character described comprising, in combination, a pair of arms each fashioned to contact an arcuate surface at two points, means for pivotally connecting said arms and constructed to permit longitudinal adjustment thereof transversely of the pivotal axis, one of said arms having a straight edge rigidly extending from its outer end on a radius through said axis, the other arm having a similar straight edge pivotally attached thereto, a rod rigid with said pivoted straight edge and slidably and pivotally supported by said means, and cooperating members for measuring the angle between said straight edges comprising an arcuate scale and a pointer, one of said members being movable with the arm having the rigid straight edge, the other member being movable angularly with said rod.

8. An instrument of the character described comprising, in combination, .a pair of arms each fashioned to contact an arcuate surface at two points, means for pivotally connecting said arms and constructed to permit longitudinal adjustment thereof transversely of the pivotal axis, one of said arms having a straight edge rigidly extending from its outer end on a radius through said axis, the other arm having a similar straight edge pivotally attached thereto, and a rod rigid with said pivoted straight edge and slidably and pivotally supported by said means to maintain the pivoted edge coincident with a radius through said axis.

9. An instrument of the character described comprising, in combination, a pair of arms each fashioned for endwise abutment with an arcuate surface at two, angularly spaced points, means for supporting said arms for pivotal and longitudinal adjustment thereof, one of said arms having a relatively fixed straight edge at its outer end extending radially from the pivotal axis and the other arm having a straight edge on the side toward the other arm to permit said straight edges to closely approach each other, the lastmentioned straight edge being pivoted to the arm to permit it to take a radial position, and means for holding the pivoted straight edge in a radial position relative to the pivotal axis of the arms in all positions of adjustment of the arms.

10. An instrument of the charaeterdescribed comprising, in combination, a pair of arms each fashioned to contact an arcuate surface at two angularly spaced points, means for supporting said arms for pivotal and longitudinal adjustment thereof, said arms having straight edges at their outer ends, and cooperating members carried by said means for measuring the angle between said straight edges, said members being fixed against angular movement relative to th respective straight edges.

11. An instrument of' the character described comprising, in combination, a pair of arms each fashioned to contact the arcuate surface at two points, a pair of slides receiving the respective arms for longitudinal adjustment, means for pivotally connecting said slides, a pair of straight edges on the outer ends of the respective arms,

and means for measuring the angle between said straight edges comprising an angular scale rigid with one of said slides to bear a fixed angular relation with one straight edge, and a pointer to cooperate with said scale pivoted on the pivotal axis of the slides and bearing a fixed angular relation to the other straight edge.

12. An instrument of the character described comprising, in combination, a pair of arms each fashioned to contact an arcuate surface at two points, a pair of channels slidably receiving said arms for longitudinal adjustment thereof, a U- shaped member pivotally supporting saidchannels between its ends, said arms respectively having a fixed straight edge and a pivoted straight edge on their outer ends, a rod rigid with said pivoted straight edge, and a part mounted on said U-shaped member to turn about the axis of said channels and slidably supporting said rod.

13. An instrument of the character described comprising, in combination, a pair of arms each adapted at one end to be placed in contact with annularly spaced points on an arcuatesurface, means connecting said arms and constructed to permit pivotal adjustment thereof about a common axis and also longitudinal adjustment trans versely of said axis, scales associated with the respective arms to permit the arms to be set at equal points of longitudinal adjustment, a pair of straight edges associated with the respective arms, one being fixed relative to its associated arm and the other being pivoted to its associated arm and being positioned on the slide toward the first arm to be able to closely approach the other straight edge as the arms are swung toward each other, and means for holding said pivoted straight edge radially of said axis comprising a rod rigid with the pivoted straight edge, a member positioned coaxially with the arms and slidably receiving said rod and means for indicating the angular relation of said arms.

HENRY FERDINAND PETERSON. 

